Rotary blower with super-charged injection cooling

ABSTRACT

This invention involves a rotary blower with super-charged injection cooling having multiple interconnected and synchronized parallel multi-lobe rotors with the same number of lobes for propelling flow from a suction port to a discharge port of an inner casing without using internal compression. The embodiments incorporate manifolds near the blower discharge port acting as super-charging inlet port injecting air at the elevated pressure over the blower discharge pressure to cool the impellers and internal casing. The cooling air supply could be piped from an external compressed air source or could be generated by one or more fans mounted on the rotors own shafts.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of mechanical vacuum pumps and blowers used in industrial and municipal applications, and more particularly relates to the double rotor multi-lobe type blowers commonly known as positive displacement rotary blowers or simply Roots blowers, and more specifically relates to a super-charging injection cooled rotary blower to reach deep vacuums between 15-28 Inch-Hg.

2. Description of the Prior Art

Rotary blowers are widely used in industrial and municipal applications. In blower terminology, for an atmospheric inlet air, when discharge pressure rise is below 5 pound per square inch gage (psig), it is termed as a fan. When the discharge pressure rise is between 5 to 25 psig, it is then called a blower. Above 25 psig belongs to the compressor range. From application point of view, if a blower inlet is connected to a vacuum while discharge is atmospheric pressure, it is specifically called an exhauster or vacuum pump and its vacuum is usually measured using inch of mercury (″ Hg, gage) as units. Another terminology often used is compression ratio, the ratio of absolute discharge pressure over absolute inlet pressure, which is the same no matter whether it is a pressure or vacuum application. Inlet vacuum from 10″ Hg all the way to 28″ Hg (gage) could be obtained with a single rotary blower and is considered as a high vacuum compared to the conventional medium vacuum of 5 to 15″ Hg. High-vacuum blowers are widely used, for example, for loading a bulk truck by pneumatic conveying of bulk materials or for municipality sewer cleaning.

Rotary blowers are particularly desired for high vacuum applications because of its unique performance characteristics inherent from its rotary positive displacement nature: it delivers an almost constant flow at varying vacuum levels. The ability of varying pressure or vacuum at a constant flow makes rotary blowers the ideal tools for pneumatic conveying applications where material clogging could be quickly cleared with the increase of the discharge pressure or suction vacuum while maintaining the transfer capability.

However, the high vacuum in 15-28″ Hg range (equivalent to the compression ratio range of 2:1 to 15:1) is difficult to obtain in a single stage compression, mainly due to the higher discharge temperature resulted from the higher compression ratio. The heat from compression alone is so great that the discharge air temperature could be over 1000 F if it is not properly cooled.

In addition, from a mechanical point of view, the raised discharge temperature reduces the internal clearances between the rotors and casing due to thermal expansion so that it could potentially cause rotor rubbing and total seizure failure. The higher temperature of discharge air also raises the temperature of bearings, timing gears and oil, shortening their life or eventually causing total failure.

Various approaches have been developed to address the higher temperature problems at high compression ratio. U.S. Pat. No. 6,817,844 disclosed a method of cooling the outer surfaces of a rotary blower, illustrated in FIGS. 1 and 2, particularly in bearing and oil reservoir area, using shaft-mounted impeller. It is effective, allowing one stage compression ratio to reach 3:1 (equivalent to 30 psig for pressure or 20″ Hg for vacuum). At this pressure ratio, the discharge air temperature is as high as 450 F while bearing and oil temp remain relatively cool. U.S. Pat. No. 3,351,227 to Weatherston and publication “Roots DVJ Dry Vacuum Whispair Blowers”, as illustrated by FIGS. 3 and 4, disclosed another method of cooling the internal impellers of Roots blower by using its own vacuum to suck in cooling air from the atmosphere at ports near discharge port. This method could achieve one-stage compression ratio up to 15:1 (equivalent to 28″ Hg inlet vacuum).

However, while Weatherston and Roots DVJ attempted to deal with the problems of higher-pressure ratio blowers, they fail to control the cooling air pressure, hence the cooling mass flow rate into the blower which is decisive for cooling purposes. This failure could lead to high bearing and oil temperatures at the highest-pressure ratio and create reliability problems.

Accordingly, it is always desirable to provide a new design and construction of high compression ratio rotary blowers that can achieve high vacuum but also effectively cool the internal rotor lobes and casing in conventional rotary blowers, so that they can operate more safely, efficiently and reliably.

SUMMARY OF THE INVENTION

The present invention is directed to a high vacuum rotary blower that utilizes manifolds as super-charging inlet ports injecting cooling air at the elevated pressure (higher than blower discharge pressure) onto impellers of the rotary blower. It would also be preferable if the present invention could cool the internal casing surfaces by directing some of the super-charging channels as induced air to carry the heat away as fast as possible from the discharge area The super-charging air could be supplied from a separate compressed air source or provided by fans mounted on the rotor own shafts.

It is an object of the present invention to provide a new and unique design and construction of a rotary blower that can achieve higher vacuum and pressure ratio than the conventional rotary blowers while not using liquid cooling methods.

It is also an object of the present invention to provide a new and unique design and construction of a rotary blower that utilizes a separate compressed air source supplying super-charging cooling air through manifolds on the casing to more effectively reduce the high temperature caused by the high compression ratio.

It is also an object of the present invention to provide a new and unique design and construction of a rotary blower that utilizes one or more fans mounted on the rotor shafts supplying super-charging cooling air through manifolds on the casing to more effectively reduce the high temperature caused by the high compression ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring particularly to the drawings for the purpose of illustration only and not limitation, there is illustrated:

FIG. 1 (PRIOR ART) is an illustrative partial cross-sectional front view of a typical arrangement of a conventional rotary blower with external forced air-cooling;

FIG. 2 (PRIOR ART) is an illustrative partial cross-sectional side view of the typical arrangement of a conventional rotary blower with external forced air-cooling;

FIG. 3 (PRIOR ART) is an illustrative partial cross-sectional front view of a typical arrangement of a conventional rotary blower with injection air-cooling at atmospheric pressure;

FIG. 4 (PRIOR ART) is an illustrative partial cross-sectional side view of the typical arrangement of a conventional rotary blower with injection air-cooling at atmospheric pressure;

FIG. 5 is an illustrative partial cross-sectional front view of a preferred embodiment of the present invention high vacuum rotary blower with super-charging injection cooling-air supplied by integral fans mounted on the rotor own shafts;

FIG. 6 is an illustrative partial cross-sectional side view of a preferred embodiment of the present invention high vacuum rotary blower with super-charging injection cooling-air supplied by integral fans mounted on the rotor own shafts;

FIG. 7 is an illustrative partial cross-sectional top view of a preferred embodiment of the present invention high vacuum rotary blower with super-charging injection cooling-air supplied by integral fans mounted on the rotor own shafts;

FIG. 8 is an illustrative partial cross-sectional front view of a preferred embodiment of the present invention high vacuum rotary blower with super-charging injection cooling by an external compressed air supply;

FIG. 9 is an illustrative partial cross-sectional side view of a preferred embodiment of the present invention high vacuum rotary blower with super-charging injection cooling by an external compressed air supply;

FIG. 10 is an illustrative partial cross-sectional top view of a preferred embodiment of the present invention high vacuum rotary blower with super-charging injection cooling by an external compressed air supply.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Although specific embodiments of the present invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims.

As a brief introduction, the present invention rotary blower with super-charged injection cooling includes an inner enclosed casing having a flow suction port and a flow discharge port and an internal bearing support structure, and an outer super-charged air cooling cover, shaped to surround the blower and to conform generally to its body contours, but is oversized to provide space for fans, cooling flow channels between outer skin of the blower and cover, and manifolds for final stage injection.

The present invention rotary blower with super-charged injection cooling also includes two parallel multi-lobe rotors mounted on two parallel rotor shafts respectively, where the rotor shafts are supported by the internal bearing support structure of the inner casing and interconnected through a set of timing gears to rotate the rotors in synchronization for propelling flow from the suction port to the discharge port. Cooling impellers are mounted on rotor shafts at locations adjacent to the inlet and outlet openings of the outer cover for circulating cooling air from an inlet filter through the flow channels between the outer cover and the blower outer skin into manifolds for final stage injection.

It is therefore an object of the present invention to teach the construction of a super-charged injection cooling for reducing the rotor and casing temperatures near blower discharge. More specifically, the super-charged injection cooling of the present invention is an apparatus constructed to engage in contact with a rotary blower so ? as to both cool the blower outer surfaces and inner surfaces by super-charged injection. The present invention rotary blower with super-charged injection cooling is capable of achieving high vacuum while maintaining being effectively cooled, light weight and compact size, thereby improving the blower reliability in mobile and industrial applications.

Referring to FIGS. 5 to 7, there is shown a typical arrangement of a prefered embodiment of the rotary blower 10 with super-charged injection cooling apparatus 50. Typically, the rotary blower 10 has two parallel rotors 12 mounted on rotor shafts 14 and 16 respectively, where rotor shaft 14 is driven by an external rotational driving mechanism (not shown) and through a set of timing gears 18 rotate the rotors 12 in synchronization without touching each other for propelling the flow from a suction port 36 to a discharge port 38 of the blower 10. The rotary blower 10 also has an enclosed casing 20, wherein the rotor shafts 14 and 16 are mounted on an internal bearing support structure 22 with bearings 24 and seals 26. The casing structure further includes a flow passage 53 as super charging air passage between the cooling fan casing and the outer casing 20 as indicated by the arrows for cooling flow direction in FIGS. 5 to 7. In FIG. 5 and 6, the arrows show the direction of the internal flow as propelled by the rotors 12 from a suction port 36 to a discharge port 38 of the blower 10.

As an important novel and unique feature of the present invention, a super-charged injection-cooling apparatus, is surrounding the rotary blower 10 of the present invention, and its cross-section is illustrated in FIG. 5 to 7. In the embodiment illustrated, super-charged injection cooling apparatus 50 is comprised of an inlet filter 52, a cooling fan 40, a super charging flow passage 53, manifolds 54 and injection ports 56 and 58. The fan 40 is employed on one side of the blower to provide positive injection cooling air for the blower 10. The cooling fan is mounted on the extended shaft 14 for bringing in cooling air from an inlet filter 52, which is in turn guided by the flow passage 53 to the inner casing 20 and into manifolds 54, gathering for injection onto impeller 12 through openings 56 and into discharge port 38 through induction openings 58, and exiting at discharge port 38, as shown by the arrows in FIGS. 5 to 7.

When a rotary blower 10 is equipped by the super-charged injection cooling apparatus 50 of the present invention, there exists both a reduction in the temperature of mechanical components such as bearings 24 and seals 26 as well as a reduction in the temperature of aero-related components such as rotors 12 and inner casing surfaces near discharge port 38 of the rotary blower.

The theory of operation underlying the super-charged injection cooling apparatus 50 of the present invention is as follows. With the fan 40 generating a higher pressure above the discharge pressure, the cooling air flow and pressure can be more effectively controlled and guided around the blower outer surfaces 20 and injected onto rotors 12 and discharge port 38 through openings 56 and 58, hence increasing the cooling mass flow rate into the blower 10 which is decisive for cooling purposes. This will lead to better bearing 24 and seal 26 lives and improve blower 10 reliability.

FIGS. 8 to 10 show a typical arrangement of another prefered embodiment of the rotary blower 10 with super-charged injection cooling apparatus 60. In this embodiment, super-charged injection cooling apparatus 60 is comprised of an external compressed air supply 70 with an inlet filter 62, a super charging flow passage 63, manifold 64 and injection ports 66 and 68. The super-charging cooling air from supply 70, is guided by flow dust 63 to the manifold 64, gathering for injection onto rotors 12 through openings 66 and into discharge port 38 through induction openings 68, exiting at discharge port 38, as shown by the arrows in FIGS. 8 to 10.

It is apparent that there has been provided in accordance with the present invention rotary blower with super-charged injection cooling for effectively reducing the high temperature caused by the high compression ratio in rotary blower. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims. 

1. A rotary blower with super-charged injection cooling apparatus, comprising: a. a housing structure having a flow suction port and a flow discharge port and internal flow passage there-between, and a manifold enclosing casing with injection ports towards rotor near discharge port; b. two parallel multi-lobe rotors having the same number of lobes and rotatably mounted on two parallel rotor shafts respectively inside said inner casing and interconnected through a set of timing gears to rotate in synchronization for propelling flow from said suction port to said discharge port; c. a super-charged apparatus comprising a cooling fan mounted on one of said rotor shaft and a flow passage for circulating cooling air through said apparatus to said manifold; d. whereby said rotary blower is capable of achieving high vacuum while being kept light in mass and small in size, and at the same time enhancing the heat transfer from said blower outer surfaces, so that they could operate more quietly, reliably and be used for mobile applications.
 2. A rotary blower with super-charged injection cooling apparatus as claimed in claim 1, wherein said discharge port has induction channels between said injection ports and said outlet flange.
 3. A rotary blower with super-charged injection cooling apparatus, comprising: a. a housing structure having a flow suction port and a flow discharge port and internal flow passage there-between, and a manifold enclosing casing with injection ports towards rotor near discharge port; b. two parallel multi-lobe rotors having the same number of lobes and rotatably mounted on two parallel rotor shafts respectively inside said inner casing and interconnected through a set of timing gears to rotate in synchronization for propelling flow from said suction port to said discharge port; c. a super-charged apparatus comprising an inlet filter, a cooling fan mounted on one of said rotor shaft and a flow passage for circulating cooling air through said apparatus to said manifold; d. whereby said rotary blower is capable of achieving high vacuum while being kept light in mass and small in size, and at the same time enhancing the heat transfer from said blower outer surfaces, so that they could operate more quietly, reliably and be used for mobile applications.
 4. A rotary blower with super-charged injection cooling apparatus as claimed in claim 3, wherein said discharge port has induction channels between said injection ports and said outlet flange.
 5. A rotary blower with super-charged injection cooling apparatus, comprising: a. a housing structure having a flow suction port and a flow discharge port and internal flow passage there-between, and a manifold enclosing casing with injection ports towards rotor near discharge port; b. two parallel multi-lobe rotors having the same number of lobes and rotatably mounted on two parallel rotor shafts respectively inside said inner casing and interconnected through a set of timing gears to rotate in synchronization for propelling flow from said suction port to said discharge port; c. a super-charged apparatus comprising said manifold, an external compressed air supply and flow passage connecting said compressed air supply and said injection manifold; d. whereby said rotary blower is capable of achieving high vacuum while being kept light in mass and small in size, and at the same time enhancing the heat transfer from said blower outer surfaces, so that they could operate more quietly, reliably and be used for mobile applications.
 6. A rotary blower with super-charged injection cooling apparatus as claimed in claim 5, wherein said discharge port has induction channels between said injection ports and said outlet flange. 